Structural Analysis of Human LonP1 Protease Bound with the Native Substrate

Area of Science:

• Mitochondrial biology
• Proteostasis
• Structural biology

Background:

• Human mitochondrial Lon protease (LonP1) is crucial for mitochondrial DNA copy number and metabolic reprogramming.
• The structural mechanisms by which LonP1 recognizes and processes its native substrates are not well understood.

Purpose of the Study:

• To elucidate the structural basis of human LonP1 substrate recognition and processing.
• To determine the high-resolution structure of the human LonP1 hexamer bound to its native substrate, TFAM.

Main Methods:

• High-resolution cryo-electron microscopy (cryo-EM) of the human LonP1-TFAM complex.
• Structural analysis of the hexameric LonP1 engaging its substrate.

Main Results:

• The cryo-EM reconstruction reveals a bipartite search-and-shred mechanism unique to human LonP1.
• The N-terminal domain (NTD) acts as a selective vestibule for substrate recruitment and initial unfolding.
• Substrate threading through the central channel involves a hand-over-hand mechanism driven by aromatic pore-loops.

Conclusions:

• The determined structure provides a mechanistic explanation for LonP1's substrate engagement and processing.
• This structural framework offers insights into targeting mitochondrial proteostasis for therapeutic interventions in human diseases.